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How to Determine Cut Glass

Cut glass is a type of glass decorated with shallow and deep cuts. One highly collectible form is American Brilliant Period glass. Pieces from this period were made between 1876 and 1917. Collectors pay thousands of dollars for rare Brilliant Period cut glass. Unfortunately, reproduction pieces have flooded the antiques market costing collectors an estimated $3 to $5 million, according to the American Cut Glass Association. New collectors will be glad to know it is possible to determine cut glass with ultraviolet light. Another option is to compare the piece in question with a piece of authentic cut glass.

Things You'll Need

Black light bulb

Instructions

- 1
  Expose the piece to a black light bulb in a dark space. Glass makers used to add manganese oxide to molten glass to improve the color quality. Under ultraviolet light, older glass pieces have a color similar to lemon-lime soda. New pieces have a pink or purple cast.
- 2
  Hold authentic cut glass in one hand and the piece in question in the opposite hand. The lead content of old glass varies from 34 to 40 percent. The lead content of new glass is consistently 24 to 25 percent. So an older piece of cut glass is heavier than a reproduction piece.
- 3
  Determine cut glass by the unadorned sections. Early artisans made incisions on plain vessels called blanks. Older blanks were hand-blown. They lack the uniformity of the modern blanks that are used in reproductions. Feel an uncut section. It is an original if it feels uneven.
- 4
  Look for grooves in the design. Early methods relied on metal, stone and wooden wheels for smooth incisions. Contemporary methods use diamond wheels, which creates grooves in the incisions.
- 5
  Examine the signature marks on cut glass. Older signature marks are clearly legible. Newer signatures are illegible because of smudge marks.
- 6
  Inspect the sides and bottom for wear. Over time glass tends to chip and scratch, especially at the base. Reproduction pieces do not show wear.
- 7
  Check for the presence of film by running your fingers across the surface. The sodium content of older pieces is only 0.1 percent, but newer pieces have up to 3 percent. The added sodium attracts moisture from the air. This causes a film to develop on the surface as opposed to a coating of dry dust.

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